BlueNRG-MS claims to support the Bluetooth Core Specification 4.2, which includes the data length extension. However, I don't find any pointers on how to enable it. For the BlueNRG-2, there appear to be special commands in the HCI LE API (see https://www.st.com/resource/en/programming_manual/dm00294449-bluenrg1-bluenrg2-ble-stack-v2x-programming-guidelines-stmicroelectronics.pdf, chapter 3.12), but I can'f find similar functions in the respective drivers for the BlueNRG-MS.
